Mitigating Pollutants from Highway Infrastructure for Total Maximum Daily Load (TMDL) Compliance: Phase I

2016Final October 1, 2014 - October 31, 2016PDFTech ReportBest practicesComplianceDebris flowsDecision support systemsGeographic information systemsHabitat (Ecology)RegulationsRunoffWater quality managementWatershedsTMDLTotal maximum daily loadsL-THIAStormwaterUnited StatesMid-Atlantic Transportation Sustainability University Transportation CenterHunter, James G.Kang, Dong HeeMorgan State UniversityUnited States. Dept. of Transportation. Office of the Secretary for Research and TechnologyUniversity Transportation Centers Program (U.S.)US Transportation CollectionThe protection of United States waters, such as the Chesapeake Bay, is of critical importance and has strategic significance to associated state transportation agencies. These organizations must assist in the effort to meet multijurisdictional stormwater regulations within the watershed. Stormwater runoff from roads and highways may carry nutrients, debris, oil, heavy metals, solids and other compounds, often directly into waterways. The resulting runoff may have detrimental pollutants that often go untreated into waters and can damage ecologically sensitive habitat. As stormwater regulations are implemented, effective guidance for understanding pollutant loadings from highway infrastructure has become essential. State transportation agencies will need additional tools to consider appropriate watershed scale impacts and evaluate actions for stormwater compliance. In this study, an amended framework for the Long-Term Hydrologic Impact Assessment Model (L-THIA) is used to determine stormwater pollutant loading from highways. The L-THIA method estimates the long-term impacts of land use on stormwater quantity and quality. The methodology is applied to estimate the average annual pollutant loading from the associated amount of impervious surface of highways. A case study demonstrates using this method to assess the average annual pollutant loading from Maryland\u2019s state roads and highways within 11 regulated counties. The results indicate that L-THIA can provide direct estimation of targeted stormwater pollutants from highways and estimate pollution reduction of best management practices